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Earth Surface Dynamics An interactive open-access journal of the European Geosciences Union

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Earth Surf. Dynam., 4, 607-625, 2016
https://doi.org/10.5194/esurf-4-607-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
01 Aug 2016
Exploring the sensitivity on a soil area-slope-grading relationship to changes in process parameters using a pedogenesis model
W. D. Dimuth P. Welivitiya1,2, Garry R. Willgoose1, Greg R. Hancock2, and Sagy Cohen3 1School of Engineering, The University of Newcastle, Callaghan, 2308, Australia
2School of Environment and Life Sciences, The University of Newcastle, Callaghan, 2308, Australia
3Department of Geography, University of Alabama, P.O. Box 870322, Tuscaloosa, Alabama 35487, USA
Abstract. This paper generalises the physical dependence of the relationship between contributing area, local slope, and the surface soil grading using a pedogenesis model and allows an exploration of soilscape self-organisation. A parametric study was carried out using different parent materials, erosion, and weathering mechanisms. These simulations confirmed the generality of the area-slope-d50 relationship. The relationship is also true for other statistics of soil grading (e.g. d10,d90) and robust for different depths within the profile. For small area-slope regimes (i.e. hillslopes with small areas and/or slopes) only the smallest particles can be mobilised by erosion and the area-slope-d50 relationship appears to reflect the erosion model and its Shield's Stress threshold. For higher area-slope regimes, total mobilization of the entire soil grading occurs and self-organisation reflects the relative entrainment of different size fractions. Occasionally the interaction between the in-profile weathering and surface erosion draws the bedrock to the surface and forms a bedrock outcrop. The study also shows the influence on different depth-dependent in-profile weathering functions in the formation of the equilibrium soil profile and the grading characteristics of the soil within the profile. We outline the potential of this new model and its ability to numerically explore soil and landscape properties.

Citation: Welivitiya, W. D. D. P., Willgoose, G. R., Hancock, G. R., and Cohen, S.: Exploring the sensitivity on a soil area-slope-grading relationship to changes in process parameters using a pedogenesis model, Earth Surf. Dynam., 4, 607-625, https://doi.org/10.5194/esurf-4-607-2016, 2016.
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Short summary
This paper generalises the physical dependence of the relationship between contributing area, local slope, and the surface soil grading first described by Cohen et al. (2009, 2010) using a soil evolution model called SSSPAM. We show the influence of weathering on the equilibrium soil profile and its spatial distribution. We conclude that the soil grading relationship is robust and will occur for most equilibrium soils. This spatial organisation is also true below the surface.
This paper generalises the physical dependence of the relationship between contributing area,...
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